只需从req.HttpContext.User.Claims对象中获取声明“http://schemas.microsoft.com/2017/07/functions/claims/keyid“，它包含键ID，以防使用功能键。
工作起来就像一个魅力，不需要外部查找。

const string KEY_CLAIM = "http://schemas.microsoft.com/2017/07/functions/claims/keyid";
public static async Task<IActionResult> Run(HttpRequest req, ILogger log)
{
    var claim = req.HttpContext.User.Claims.FirstOrDefault(c => c.Type == KEY_CLAIM);
    if (claim == null) 
    {
        log.LogError("Something went SUPER wrong");
        throw new UnauthorizedAccessException();
    }
    else
    {
        log.LogInformation( "Processing call from {callSource}", claim.Value);
    }

Sajeetharan回答了如何使用REST API获取密钥。
关于使用RBAC的能力，您需要使用托管身份，您可以找到有关如何设置它的详细信息：https://learn.microsoft.com/en-us/azure/app-service/overview-managed-identity?tabs=dotnet

在Azure Functions v1中：

[FunctionName("MyAuthenticatedFunction")]
public static async Task<HttpResponseMessage> MyAuthenticatedFunction([HttpTrigger(AuthorizationLevel.Function)] System.Net.Http.HttpRequestMessage reqMsg, ILogger log)
{
    if (reqMsg.Properties.TryGetValue("MS_AzureFunctionsKeyId", out object val))
        log.LogInformation($"MS_AzureFunctionsKeyId: {val}");  
}

代码参考：WebJobs.Script.WebHost/Filters/AuthorizationLevelAttribute.cs#L77